Virtual semiconductor nanowire, and methods of using same

ABSTRACT

A multiple-gate field-effect transistor includes a fluid in a top gate, two lateral gates, and a bottom gate. The multiple-gate field-effect transistor also includes a patterned depletion zone and a virtual depletion zone that has a lesser width than the patterned depletion zone. The virtual depletion zone width creates a virtual semiconductor nanowire that is lesser in width than the patterned depletion zone.

RELATED APPLICATIONS

This is a Divisional of patent application Ser. No. 12/156,361, filed onMay 30, 2008, now U.S. Pat. No. 8,007,727.

TECHNICAL FIELD

Disclosed embodiments relate to semiconductive apparatus and methods ofusing them.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the manner in which embodiments are obtained, amore particular description of various embodiments briefly describedabove will be rendered by reference to the appended drawings. Thesedrawings depict embodiments that are not necessarily drawn to scale andare not to be considered to be limiting in scope. Some embodiments willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIG. 1 is a cross-section elevation of a multiple-gate field-effecttransistor according to an embodiment;

FIG. 2 is a top plan of the multiple-gate field-effect transistordepicted in FIG. 1 according to an example embodiment;

FIG. 3 a is a cross-section elevation of a multiple-gate field-effecttransistor according to an embodiment;

FIG. 3 b is a cross-section elevation of the multiple-gate field-effecttransistor depicted in FIG. 3 a during a method according to anembodiment;

FIG. 4 is a method flow diagram 400 according to an embodiment; and

FIG. 5 is a schematic of an electronic system according to anembodiment.

DETAILED DESCRIPTION

A multiple-gate field-effect transistor (MUGFET) includes a fluid topgate to receive a biological product, and the MUGFET also includes avirtual depletion zone within a patterned depletion zone. The virtualdepletion zone has a width that is less than the patterned depletionzone.

The following description includes terms, such as upper, lower, first,second, etc. that are used for descriptive purposes only and are not tobe construed as limiting. The embodiments of an apparatus or articledescribed herein can be manufactured, used, or shipped in a number ofpositions and orientations.

Reference will now be made to the drawings wherein like structures maybe provided with like suffix reference designations. In order to showthe structures of various embodiments most clearly, the drawingsincluded herein are diagrammatic representations of integrated circuitstructures. Thus, the actual appearance of the fabricated structures,for example in a photomicrograph, may appear different while stillincorporating the claimed structures of the illustrated embodiments.Moreover, the drawings show only the structures necessary to understandthe illustrated embodiments. Additional structures known in the art havenot been included to maintain the clarity of the drawings.

FIG. 1 is a cross-section elevation of a multiple-gate field-effecttransistor (MUGFET) 100 according to an embodiment. A semiconductivewell 110 includes a patterned depletion zone 112 and a virtual depletionzone 114. The patterned depletion zone 112 includes a first width 116and the virtual depletion zone 114 includes a second width 118. Duringoperation of the MUGFET, the second width 118 is less than the firstwidth 116.

The MUGFET 100 also includes a first lateral gate 120 and a secondlateral gate 122. The respective first- and second lateral gates 120 and122 are connected to the diffusion terminals 128. The respective first-and second lateral gates 120 and 122 may be situated with a passivationlayer 126 such as a polyimide material or a polyamide material. Othermaterials may be used for the passivation layer 126.

In an embodiment, the semiconductive well 110 is part of a largersemiconductive structure such as an epitaxial semiconductor material ora semiconductor on insulator (SOI) material. In an embodiment, thesemiconductive well 110 is differently doped than lateral structuressuch as lateral implant regions 128.

In an embodiment, a bottom gate 130 is disposed below the semiconductivewell 110 and it is insulated from the semiconductive well 110 with abottom gate dielectric 132. In an embodiment, the bottom gate 130 ismetallic. In an embodiment, the bottom gate 130 is polycrystalline.

In an embodiment, a reference electrode 136 interface the electricallyconductive fluid 137 and acts as the top gate includes a top electrode.The electrically conductive fluid 137 may be a liquid or a vapor or agas. Capture molecules 140 are coupled on the dielectric layer, 138.Additionally, the top gate includes an electrically conductive fluid 137that immerses the capture molecule 140 and at least a portion of the topelectrode 136. In an embodiment, the capture molecule 140 is a specificreceptor for a biological product such as an antibody that has beendeveloped to adhere to the top gate dielectric 138 and to be selectivefor capturing only analytes. Consequently, a label-free protein analysismethod is achieved by using the MUGFET 100 with a virtual channel 114that is the virtual depletion zone. In an embodiment, the system ofanalyte and capture molecule may be complementary type such as anorganic system or an inorganic system.

The virtual depletion zone 114 fits entirely within the confines of thepatterned depletion zone 112, and that has a virtual width 118 that isless than the patterned width 116. In an embodiment, a material such asa DNA sample is bonded to the capture molecule 140 in such a way that agiven DNA sequence is identified. For example, the capture molecule 140may be a complementary sequence for a DNA segment in electricallyconductive fluid 137. In an example embodiment, immunosensing isperformed where the capturing molecule is an antibody. In this examplethe analyte can be any molecule with antibody-antigen affinity such asprostrate specific antigen (PSA) or breast cancer (BRC).

FIG. 1 also depicts a specific analyte 142 one of which is referencedwith the reference numeral 142. The specific analyte 142 has beencaptured by the capture molecule 140 such that performance of the MUGFET100 is affected by the amount of analyte 142 that has been captured. Forexample, the potential that may be experienced by the MUGFET 100 atgiven overall amount of gate current and/or gate potential, can allowquantitative analysis of the presence of the analyte 142. In anembodiment, the analyte 142 binds with a carrier such as a light-activecomposition, and the presence of the analyte 142 is measured by opticalanalysis in relationship to the top gate.

In an embodiment, operation of the MUGFET 100 is carried out such thatthe virtual depletion zone 114 forms a virtual semiconductor nanowire114 between a source and drain in the patterned depletion zone 112 ofthe MUGFET 100. The virtual width 118 of the virtual semiconductornanowire 114 is less than the patterned width 116 in the semiconductivewell 110. The virtual semiconductor nanowire 114 may have a more usefulsensitivity to current and potential than the MUGFET with only thepatterned width 116. This enhanced sensitivity may allow for more usefulanalysis of biological products.

In an embodiment, the patterned width 116 is in a range from about 2nanometers (nm) to about 50 nm, and the virtual semiconductor nanowire114 has a virtual width 118 that is less than the patterned width 116.For example, where the patterned width 116 of the patterned depletionzone 112 is unity, the virtual width 118 is about 20% of the patternedwidth. In an embodiment, where the patterned width 116 of the patterneddepletion zone 112 is unity, the virtual width 118 is about 40% of thepatterned width. In an embodiment, where the patterned width 116 of thepatterned depletion zone 112 is unity, the virtual width 118 is about60% of the patterned width. In an embodiment, where the patterned width116 of the patterned depletion zone 112 is unity, the virtual width 118is about 80% of the patterned width. In an embodiment, where thepatterned width 116 of the patterned depletion zone 112 is unity, thevirtual width 118 is about 10% of the patterned width. In an embodiment,the patterned width 116 is in a range from about 50 nm to about 250 nm.

FIG. 2 is a top plan of the multiple-gate field-effect transistor 100depicted in FIG. 1 according to an example embodiment. Thesemiconductive well 110 includes the patterned depletion zone 112 andthe virtual depletion zone 114. The MUGFET 100 also includes the firstlateral gate 120 and the second lateral gate 122. The respective first-and second lateral gates 120 and 122 are disposed above the lateralimplant regions 128, which are depicted in phantom lines since they areobscured by the passivation layer 126 (FIG. 1).

A MUGFET source electrode 144 is depicted in contact with a sourceregion 146, and a MUGFET drain electrode 148 is depicted in contact witha drain region 150.

During operation of the MUGFET 100, analyte 142 are interacting with acapture molecule (see FIG. 1). According to an embodiment, analysis forthe analyte 142 is focused only on analyte 142 that has adsorbed ontocapture molecules that are above the virtual depletion zone 114.Consequently, analysis of the content of biological products in thefluid portion 137 of the top gate is carried out. Because analysis isrestricted to adsorbed analyte 142 only above the virtual depletion zone114, the analysis may be more useful than when analysis is carried outabove the entire patterned depletion zone 112. In FIG. 2 it can be seenthat there are four analytes 142 above the virtual depletion zone 114,one occurrence of which is noted with the reference number 142.

FIG. 3 a is a cross-section elevation of a multiple-gate field-effecttransistor 300 according to an embodiment. A semiconductive well 310includes a patterned depletion zone 312 and a virtual depletion zone 314that forms an arbitrary cross section; in the illustration, thearbitrary cross section is circular. The patterned depletion zone 312includes a first width 316 and the virtual depletion zone 314 includes asecond width 318. During operation of the MUGFET 300, the second width318 is less than the first width 316. Consequently, a virtualsemiconductor nanowire exists in the form of the virtual depletion zone314 that has been imposed within the patterned depletion zone 312.

The MUGFET 300 also includes a first lateral gate 320 and a secondlateral gate 322. The respective first- and second lateral gates 320 and322 are that rests upon a top surface of the semiconductive materialthat includes the semiconductive well 310. The respective first- andsecond lateral gates 320 and 322 may be situated with a passivationlayer 326 such as a polyimide material or a polyamide material. Othermaterials may be used for the passivation layer 326.

In an embodiment, the semiconductive well 310 is part of a largersemiconductive structure such as an epitaxial semiconductor material ora semiconductor on insulator (SOI) material. In an embodiment, thesemiconductive well 310 is differently doped than lateral structuressuch as a lateral implant regions 328.

In an embodiment, a bottom gate 330 is disposed below the semiconductivewell 310 and it is insulated from the semiconductive well 310 with abottom gate dielectric 332. Vertical positioning of the virtualdepletion zone 314 within the semiconductive well 310, as well aslateral dimensions of the virtual depletion zone 314 may be affected bythe bottom gate 330 as well as the other gates 320, 322, and the topgate.

In an embodiment, the top gate includes a top electrode 336, a top gatedielectric 338, and a capture molecule 340. Additionally, the top gateincludes an electrically conductive fluid 337 that immerses the capturemolecule 340 and at least a portion of the top electrode 336.

FIG. 3 b is a cross-section elevation of the multiple-gate field-effecttransistor 300 depicted in FIG. 3 a during a method according to anembodiment. The MUGFET 301 is being operated such that the virtualdepletion zone 315 has taken on a different oval shape in compared tothe virtual depletion zone 314 depicted in FIG. 3 a. Consequently, anoval-shaped virtual semiconductor nanowire exists in the form of thevirtual depletion zone 315 that has been imposed within the patterneddepletion zone 312.

In an embodiment, the semiconductive well 310 has a characteristicheight 352 and the virtual depletion zone 315 is centered at a virtualdepletion zone height 353. As illustrated and in an embodiment, thevirtual depletion zone height 353 is below the middle of thecharacteristic height 352 of the semiconductive well 310. This locationof the depletion zone height 353 may be referred to as“non-symmetrically vertical”. In an embodiment, background andoperational signal noise is reduced during analytical use of the MUGFET301 when the virtual depletion zone height 353 is below the middle ofthe characteristic height 352 of the semiconductive well 310 (notnecessarily below middle!). This location of the depletion zone height353 may also be referred to as “non-symmetrically vertical”.

In an embodiment, the virtual depletion zone height 353 is below themiddle of the characteristic height 352 of the semiconductive well 310.In an embodiment, the virtual depletion zone height 353 is above themiddle of the characteristic height 352 of the semiconductive well 310.Consequently, a non-symmetrically vertically positioned virtualsemiconductor nanowire exists in the form of the virtual depletion zone315 that has been imposed within the patterned depletion zone 312

In an embodiment, the aspect ratio of the virtual depletion zone 315 isaffected by gate voltage within the bottom gate 330 as well as the othergates 320, 322, and the top gate. As depicted in FIG. 3 b, the aspectratio of the virtual depletion zone 315 is a flattened oval such thatthe second width 318 if it is unity is greater than a virtual depletionzone height 319. Consequently, the aspect ratio, height divided bywidth, is less than one. In an embodiment, the aspect ratio is equal toone. In an embodiment, the aspect ratio is greater than one. Aspectratio is also measured by a comparison of at least one of current andpotential in the lateral gates 320 and 322 to at least one of thecurrent and potential in the top gate and the bottom gate 330.

In an embodiment, a non-symmetrically vertically positioned andeccentric virtual semiconductor nanowire exists in the form of thevirtual depletion zone 315 that has been imposed within the patterneddepletion zone 312. Consequently, the location of the virtual depletionzone 315 is programmable. Further, the effective size of the virtualdepletion zone 315 is also programmable. In a method embodiment, an FETis first operated and checked against a standard. Next, the virtualdepletion zone, e.g., virtual depletion zone 315 is second establishedin a different area of the well and checked against both the standardand the first virtual depletion zone. As a result, the practicalscreening of the location and effective size of the virtual depletionzone 315 can lead to a more useful signal-to-noise ratio because ionpenetration into the conductive channel reduces the noise.

By reading this disclosure, one of ordinary skill in the art willappreciate the virtual nanowire can be constructed in any of severalfield-effect transistor structures, including gate all around (GAA) FET,a quadruple gate FET, a four-gate FET, a pi gate FET, a cylindrical gateFET, an omega gate FET, a triple gate FET, and fin FET.

FIG. 4 is a method flow diagram 400 according to an embodiment.

At 410, the method includes imposing a virtual channel within apatterned depletion zone of a MUGFET.

At 412, the method includes shaping the virtual channel to be eccentric.In an embodiment, shaping is done to achieve a more useful virtualchannel such that a greater sensitivity is achieved than withoutshaping. In an embodiment, the method commences at 410, passes through412, and terminates at 420.

At 414, the method includes positioning the virtual channel to benon-symmetrically vertical. In an embodiment, the method commences at410, passes through 414, and terminates at 420. In an embodiment, themethod commences at 410, passes through each of 412 and 414, andterminates at 420.

At 420, the method includes analyzing a biological product by use of thetop gate of the MUGFET. As set forth in this disclosure, analysis mayinclude a label-free protein analysis method is achieved by using aMUGFET embodiment that uses a fluid portion of a top gate that carriesan analyte of the biological product.

FIG. 5 is a schematic of an electronic system 500 according to anembodiment. The electronic system 500 as depicted can embody a MUGFETwith a fluid top electrode and a virtual channel computing system as setforth in this disclosure. In an embodiment, the electronic system 500 isa computer system that includes a system bus 520 to electrically couplethe various components of the electronic system 500. The system bus 520is a single bus or any combination of busses according to variousembodiments. The electronic system 500 includes a voltage source 530that provides power to the integrated circuit 510. In some embodiments,the voltage source 530 supplies current to the integrated circuit 510through the system bus 520.

The integrated circuit 510 is electrically coupled to the system bus 520and includes any circuit, or combination of circuits according to anembodiment. In an embodiment, the integrated circuit 510 includes aprocessor 512 that can be of any type. As used herein, the processor 512may mean any type of circuit such as, but not limited to, amicroprocessor, a microcontroller, a graphics processor, a digitalsignal processor, or another processor. Other types of circuits that canbe included in the integrated circuit 510 are a custom circuit or anASIC, such as a communications circuit 514 for use in wireless devicessuch as cellular telephones, pagers, portable computers, two-way radios,and similar electronic systems. In an embodiment, the processor 510includes on-die memory 516 such as SRAM. In an embodiment, the processor510 includes on-die memory 516 such as eDRAM.

In an embodiment, the electronic system 500 also includes an externalmemory 840 that in turn may include one or more memory elements suitableto the particular application, such as a main memory 542 in the form ofRAM, one or more hard drives 544, and/or one or more drives that handleremovable media 546, such as diskettes, compact disks (CDs), digitalvideo disks (DVDs), flash memory keys, and other removable media knownin the art.

In an embodiment, the electronic system 500 also includes a displaydevice 550, an audio output 560. In an embodiment, the electronic system500 includes a controller 570, such as a keyboard, mouse, trackball,game controller, microphone, voice-recognition device, or any otherdevice that inputs information into the electronic system 500.

As shown herein, the integrated circuit 510 can be implemented in anumber of different embodiments, including an electronic package, anelectronic system, a computer system, one or more methods of fabricatingan integrated circuit, and one or more methods of fabricating anelectronic assembly that includes the integrated circuit and the virtualnanowire MUGFET chip as set forth herein in the various embodiments andtheir art-recognized equivalents. The elements, materials, geometries,dimensions, and sequence of operations can all be varied to suitparticular packaging requirements.

The Abstract is provided to comply with 37 C.F.R. §1.72(b) requiring anabstract that will allow the reader to quickly ascertain the nature andgist of the technical disclosure. It is submitted with the understandingthat it will not be used to interpret or limit the scope or meaning ofthe claims.

In the foregoing Detailed Description, various features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments of the inventionrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter lies in lessthan all features of a single disclosed embodiment. Thus the followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separate preferred embodiment.

It will be readily understood to those skilled in the art that variousother changes in the details, material, and arrangements of the partsand method stages which have been described and illustrated in order toexplain the nature of this invention may be made without departing fromthe principles and scope of the invention as expressed in the subjoinedclaims.

1. A method comprising: analyzing a biological product at a top gate ofa multiple-gate field-effect transistor (MUGFET), wherein the MUGFETincludes: a first lateral gate and a second lateral gate disposed onopposite sides of a semiconductive well; a top gate and a bottom gatedisposed respectively above and below the semiconductive well, whereinthe top gate contains a capture molecule disposed within the top gateand an electrically conductive fluid to receive a biological productand; a source region and a drain region disposed on opposite sides ofthe semiconductive well; a patterned depletion zone between the firstand second lateral gates, wherein the patterned depletion zone includesa first width; and a virtual depletion zone imposed in thesemiconductive well, wherein the virtual depletion zone includes asecond width that is less than the first width, and wherein analyzingincludes detecting a voltage proportional to the presence of thebiological product in the electrically conductive fluid of the top gate.2. The method of claim 1, wherein analyzing includes first imposing thevirtual depletion zone into an eccentric shape within the semiconductivewell.
 3. The method of claim 1, wherein analyzing includes firstimposing the virtual depletion zone as a non-symmetrically verticallyimposed depletions zone within the semiconductive well.
 4. The method ofclaim 1, wherein analyzing includes first imposing the virtual depletionzone into a non-symmetrical shape within the semiconductive well andimposing the virtual depletion zone as a non-symmetrically verticallyimposed depletions zone within the semiconductive well.
 5. The method ofclaim 1, wherein analyzing includes monitoring at least one of potentialand current within the virtual depletion zone.